1. Field of the Invention
This disclosure relates generally to electrical circuits, and more particularly to a radio frequency (RF) transmission apparatus with reduced power consumption.
2. Description of Related Prior Art
FIG. 1, panel A, depicts a top view of a conventional wireless communication device 100. Common wireless communication devices include cellular phones, wireless networking devices, wireless handsets, personal digital assistants (PDAs), laptop and desktop computers, routers, and key fobs. As shown, the wireless communication device 100 includes a battery 102, a digital signal processor (DSP) 104, a transceiver 106, a power amplifier 108, an antenna 110, and other electronic circuitry 112. The battery 102 provides direct current (DC) power to other device components. The digital signal processor (DSP) 104 manipulates communication signals between analog and digital signal processing domains, while the transceiver 106 up and down converts the communication signals between low frequencies and RF frequencies. The power amplifier 112 amplifies a power of the signal output from the transceiver to drive a transmission signal into the antenna 110. In turn, the antenna 110 transmits the transmission signal into free space. A receiver of another wireless communication device (not shown) may receive the radiated signal through a receiver antenna and process the received signal, thus allowing wireless communication of information between the wireless communication device 100 and the other wireless communication device.
Panel B depicts a side view of the conventional wireless communication device 100. As shown, the antenna 110 and electronic circuitry components 140 (e.g., the DSP 104, the transceiver 106, etc.) are mounted on a substrate 130 such as a printed circuit board (PCB). In addition, the wireless communication device 100 includes an electrical shield 150 which can serve two purposes: (1) preventing internally generated electrical signals from radiating out to affect the function of other components; and (2) preventing externally generated electrical signals from radiating in to affect the function of the components 140.
FIG. 2 depicts an enclosure of a convention wireless communication device. Panel A shows a wireless phone device 200 and panel B shows a wireless tablet device 250. As illustrated in panel A, the wireless phone device 200 includes antenna(s) 210 for transmitting and/or receiving radio frequency signals. The wireless phone device 200 further includes a key pad 220 for tactile input and a display screen 230 for display and/or tactile input. Although a physical key pad 220 is shown, the wireless phone device 200 may alternatively include a virtual key pad (not shown), which is a software component that permits key stokes to be made via, e.g., a touch screen. In addition, the wireless phone device 200 includes casing which holds all the electronic components and component mounting substrates of the wireless phone device 200. The casing may also electrically isolate the internal components of the wireless phone device 200 from the exterior. A back cover (not shown) of the wireless phone device 200 may also include casing made from various materials. Similarly, the wireless tablet device 250 includes antenna(s) 260, a key pad 270 (or a virtual keypad), and a display screen 280 which may generally perform the same functions as the antenna(s) 210, the key pad 220, and the display screen 230 of the wireless phone device 200. In addition, the wireless tablet device 250 may also include a casing that encloses electronic components and component mounting substrates and electrically insulates these components, as well as a back cover.